1. Technical Field
The present disclosure relates to detection circuits, and especially to a fault detection circuit.
2. Description of Related Art
Referring to FIG. 8 and FIG. 9, a commonly used fault detection circuit 1 is connected to an inverter circuit 2 with a plurality of outputs, to detect whether one or more of the outputs of the inverter circuit 2 are faulty. The outputs of the inverter circuit 2 are divided into two groups. The inverter circuit 2 drives a light source module 22, and comprises a transformer unit 21 and a protection unit 23. The fault detection circuit 1 comprises a magnetic unit 11 and a signal detection unit 12.
The magnetic unit 11, connected to the inverter circuit 2, determines whether one or more of the outputs of the inverter circuit 2 are faulty, and comprises a first magnetic winding 111, a second magnetic winding 112 and a third magnetic winding 113.
The first magnetic winding 111 is connected to one group output of the inverter circuit 2, and the second magnetic winding 112 is connected to another group output of the inverter circuit 2. In addition, wrapping directions of the first magnetic winding 111 and the second wrapping winding 112 are opposite. Thus, when one or more of the outputs of the inverter circuit 2 are faulty, total flux generated by the first and second magnetic windings 111, 112 cannot be canceled out. Accordingly, the third magnetic winding 113 generates a detection signal. The signal detection unit 12 generates an abnormal signal according to the detection signal, and outputs the abnormal signal to the protection unit 23. The protection unit 23 protects the inverter circuit 2.
However, when the number of abnormal lamps of the light source module 22 corresponding to the two groups of output of the inverter circuit 2 are the same, flux generated by the first and second magnetic windings 111, 112 is the same and can also be canceled out. In this instance, the third magnetic winding 113 detects no flux and does not generate the abnormal signal, thus, the abnormal of the inverter circuit 2 is not detected.